Xerox Reference No. D/A0639A system and method for improving xerographic halftoning by magnifying a threshold array, interpolating the in-between values, enabling multiple thresholds to be accessed simultaneously and presented to multiple comparators, to cause multi-bit output. A threshold array is sampled at distinct locations separated by the sparse sampling distance to allow warping of the threshold array dots by adjusting the sampling distance in small, fractional portions (deltas) of the magnified distance. By adding more thresholds, amplitude or intensity modulation is used to move dot edges in a process direction for further flexibility in printing irrational or warpable screens.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method for generating a multi-bit output sampled threshold array halftone image from grayscale data, comprising: determining a grayscale image value to be represented by a binary clustered halftone dot, determining a nominal halftone dot shape within a halftone memory cell based on the determined grayscale image value using a threshold array, accessing multiple thresholds to obtain a multi-bit output sub-sample of the threshold array at the resolution of the image, and presenting the halftone image.
2. The method of claim 1 , wherein accessing thresholds is done using multiple comparators.
3. The method of claim 1 , wherein the sampling resolution of the threshold array is higher than the resolution of the image.
4. The method of claim 1 , wherein the sampling resolution is the resolution of the image.
5. A method for generating a multi-bit output sampled threshold array halftone image from grayscale data, comprising: determining a grayscale image value to be represented by a binary clustered halftone dot; determining a nominal halftone dot shape within a halftone memory cell based on the determined grayscale image value using a threshold array; and sub-sampling the halftone cell at something other than an integer increment; and presenting the halftone image.
6. The method of claim 5 , further comprising adjusting the sampling distance in small magnified increments of a magnified distance to permit warping of threshold array halftone dots.
7. The method of claim 5 , further comprising adding thresholds to the threshold array to permit amplitude or intensity modulation can be used to move edges in the slow scan or process direction.
8. The method of claim 5 , wherein the subsampling involves an enlarged or magnified increment from pixel to pixel.
9. The method of claim 8 , wherein the enlarged increment from pixel to pixel is an integer.
10. The method of claim 8 , wherein the enlarged increment from pixel to pixel is a non-integer.
11. The method of claim 5 , further comprising interpolating threshold values in between magnified threshold array locations.
12. The method of claim 5 , further comprising using pulse amplitude modulation to move a halftone dot shape in a slow scan direction.
13. A method for generating a multi-bit output sampled threshold array halftone image from grayscale data, comprising: determining a grayscale image value to be represented by a binary clustered halftone dot; determining a nominal halftone dot shape within a halftone memory cell based on the determined grayscale image value using a threshold array; sub-sampling the threshold array at distinct locations separated by a magnified distance; and presenting the halftone image.
14. The method of claim 13 , further comprising adjusting the sampling distance in at least one fractional distance portion of the magnified distance.
15. An apparatus that generates a multi-bit output sampled threshold array halftone image from grayscale data, comprising: an intensity determiner that determines a grayscale image value to be represented by the binary halftone dot; a shaper that determines a nominal halftone dot shape within a halftone cell based on the determined grayscale image value using a threshold array; and a comparator to sub-sample the halftone cell at something other than an integer increment.
16. An apparatus that generates a multi-bit output sampled threshold array halftone image from grayscale data, comprising: an intensity determiner that determines a grayscale image value to be represented by the binary halftone dot; a shaper that determines a nominal halftone dot shape within a halftone cell based on the determined grayscale image value using a threshold array, and at least one comparator that accesses multiple thresholds and that compares the grayscale image value to the accessed threshold values of the threshold array to obtain a multi-bit output.
17. The apparatus of claim 16 , further comprising a sub-sampler which samples the threshold array at distinct array locations separated by a magnified sampling distance.
18. The apparatus of claim 17 , further comprising an adjustor that adjusts the sampling distance in at least one fractional distance portion of the magnified distance.
19. The apparatus of claim 17 , further comprising an interpolator which interpolates threshold values in between magnified threshold array locations.
20. The apparatus of claim 16 , further comprising an adder that adds more thresholds to the threshold array.
21. The apparatus of claim 16 , further comprising a modulator that uses amplitude or intensity modulation to move a halftone dot shape in a process direction.
22. An apparatus for generating a sampled threshold array halftone image from grayscale data, comprising: a setter that sets a halftone sampling distance for a threshold array to a value greater than one; an interpolator that interpolates values within the threshold array with the altered sampling distance from halftone dot shape functions; and a sub-sampler that samples halftone threshold locations by an increment of other than one to produce a halftone dot image.
23. The apparatus of claim 22 , wherein the increment is ten.
24. The apparatus of claim 22 , wherein the increment is 3.1.
25. The apparatus of claim 22 , wherein the increment is x.9 where x is an integer.
26. The apparatus of claim 22 , wherein the increment is x.1 where x is an integer.
27. The apparatus of claim 22 , further comprising a warper that warps the sampling increment.
28. The apparatus of claim 22 , further comprising a multiple threshold accessor that accesses multiple threshold array values from the interpolator to produce multi-bit output.
29. The apparatus of claim 28 , further comprising multiple comparators that receive multiple thresholds accessed by the multiple threshold accessor.
30. The apparatus of claim 22 , further comprising a thresholder that adds halftone thresholds to moves halftone dot edges using amplitude or intensity modulation of the halftone dots.
31. A method of generating a sampled threshold array halftone image from grayscale data, comprising: setting a halftone sampling distance for a threshold array to a value greater than one; interpolating values within the threshold array with the altered sampling distance from halftone dot shape functions; sub-sampling halftone threshold locations by an increment of other than one to produce a halftone dot image; and presenting the halftone image.
32. The method of claim 31 , wherein the increment is ten.
33. The method of claim 31 , wherein the increment is 3.1.
34. The method of claim 31 , wherein the increment is x.9 where x is an integer.
35. The method of claim 31 , wherein the increment is x.1 where x is an integer.
36. The method of claim 31 , further comprising warping the sampling increment.
37. The method of claim 31 , further comprising accessing multiple threshold array values to produce multi-bit output.
38. The method of claim, 31 , further comprising: accessing multiple thresholds; and presenting the accessed multiple thresholds to multiple comparators.
39. The method of claim 31 , further comprising: adding halftone thresholds; and moving halftone dot edges using amplitude or intensity modulation of the halftone dots.
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January 15, 2003
April 15, 2008
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